In-wheel motor and electrically driven vehicle

ABSTRACT

The in-wheel motor for installation inside a wheel disk of a wheel includes: a cylindrical coil body; a coil body support member fixed to a shaft; an outer yoke that is disposed on an outer circumferential side of the coil body, and is fixed to a wheel disk; a cylindrical inner yoke that is disposed on an inner circumferential side of the coil body, and is rotatable around the shaft; and a magnet that is fixed on one of an inner circumferential face of the outer yoke and an outer circumferential face of the inner yoke, the magnet disposed to face a circumferential face of the coil body.

This application is a continuation of application Ser. No. 14/341,535, filed Jul. 25, 2014, which is a continuation in part of application Ser. No. 13/174,583, filed Jun. 30, 2011, now U.S. Pat. No. 8,820,448 B2, which is based on and claims the benefit of priority from Japanese Patent Application No. 2010-152109, filed on 2 Jul. 2010, the contents of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an in-wheel motor that drives a wheel by a motor provided inside a wheel disk of the wheel, and particularly relates to an electrically driven vehicle such as an electric car, a hybrid car and a power-assisted bicycle.

2. Related Art

Patent Document 1 (Japanese Unexamined Patent Application, Publication No. H11-262101) discloses that an iron core and a coil wound around the iron core are provided on an inner circumferential face of an outer yoke (a motor container) that is fixed to a shaft, a magnet facing the iron core is rotatably provided to the shaft, and a current is applied to the coil, thereby rotationally driving a wheel disk together with the shaft. The technique of Patent Document 1 discloses that the brake disk is fixed to the shaft between the wheel disk and the outer yoke.

Patent Document 2 (U.S. Pat. No. 7,735,588 B2) discloses an invention including: an outer yoke fixed to a wheel disk; and an inner yoke being rotatable relative to the outer yoke, in which an iron core and a coil wound around the iron core are fixed to the inner yoke, a magnet facing the iron core is fixed to the outer yoke, and an electric current is applied to the coil, thereby rotationally driving the wheel disk together with the outer yoke. In addition, Patent Document 2 discloses that a base of a brake disk support is fixed to the wheel disk via a hub, a tip of the brake disk support is disposed inside the inner yoke, the brake disk is fixed to the tip of the brake disk support, and the brake disk and a caliper are provided on an inner circumferential side of the inner yoke.

SUMMARY OF THE INVENTION

However, in Patent Document 1, since the brake disk is provided between the outer yoke and the wheel disk, space for the brake mechanisms (such as the brake disk and the caliper) are required inside the wheel disk in addition to the space for the motor mechanism; therefore, there is a problem that restriction is imposed on the space for the motor mechanism.

In Patent Document 2, a brake mechanism is provided on an inner circumferential side of an inner yoke, but a base of a brake disk support is fixed to a wheel disk via a hub, and a tip thereof is disposed on the inner yoke to fix the brake disk; therefore, there is a problem that the configuration is complicated.

Moreover, in Patent Document 2, the brake mechanism is disposed on the inner circumferential side of the motor mechanism inside the wheel disk, but the motor mechanism and the brake mechanism are separately configured; therefore, there is a problem that restriction is imposed on the space for the motor mechanism.

Furthermore, both Patent Documents 1 and 2 disclose a motor of a core type in which a coil is wound around an iron core; therefore, there is a problem that the weight is increased.

Accordingly, an object of the present invention is to provide an in-wheel motor and an electrically driven vehicle being lightweight, with a brake mechanism, without imposing any restriction on space for installing a motor mechanism.

In order to achieve such an object, a first aspect of the present invention is to provide an in-wheel motor installed inside a wheel disk of a wheel to rotationally drive the wheel around a shaft of the wheel by way of applying a current thereto, and the in-wheel motor includes: a cylindrical coil body to which a lead wire for applying a current is connected, the shaft being inserted in an inner circumferential side of the coil body; a coil body support member that is fixed to the shaft to support the coil body; a cylindrical outer yoke that is disposed on an outer circumferential side of the coil body, and is fixed to the wheel disk; a magnet that is fixed on an inner circumferential face of the outer yoke, and is disposed to face an outer circumferential face of the coil body; a cylindrical inner yoke that is disposed on the inner circumferential side of the coil body, and is disposed to face an inner circumferential face of the coil body, the inner yoke being fixed to the outer yoke and being rotatable around the shaft; a brake disk that is fixed to an inner circumferential side of the inner yoke; and a caliper that is provided on the inner circumferential side of the inner yoke to brake the brake disk.

According to the first aspect of the present invention, the motor mechanism installed inside the wheel disk is a motor mechanism of a so-called coreless type without an iron core; therefore, it is possible to provide an in-wheel motor that is more lightweight than a motor of a core type having an iron core such as those in Patent Documents 1 and 2.

It should be noted that the motor mechanism is configured with the coil body, the outer yoke, the inner yoke and the magnet; and the brake mechanism is configured with the brake disk and the caliper.

Since the brake mechanism is disposed inside the motor mechanism, the entire space inside the wheel disk can be utilized as the motor mechanism without imposing any restriction on the motor mechanism.

Since the brake disk support is directly fixed to the inner yoke as an operation member configuring the motor mechanism, a simple configuration can be achieved.

In the first aspect of the present invention, it is preferable that the outer yoke and the inner yoke together cover an outer circumferential side face, an inner circumferential side face, and one edge of the cylindrical coil body.

Since the outer yoke and the inner yoke cover the coil body, it is possible to prevent water and foreign matter from adhering thereto.

Moreover, in the first aspect of the present invention, it is preferable that the in-wheel motor further includes a caliper support disk, to which the caliper is mounted, and which is fixed to the shaft, in which a vent hole is formed in the wheel disk in a position facing an end portion of the shaft, the caliper support disk is disposed to face the vent hole of the wheel disk, and an outer diameter of the caliper support disk is larger than that of the vent hole of the wheel disk.

With such a configuration, by taking in air through the vent hole of the wheel disk, it is possible to cool the inside of the motor. The caliper support disk faces the vent hole, and the outer diameter thereof is larger than that of the vent hole; therefore, even in a case of taking in air from outside through the vent hole, it is possible to prevent water and foreign matter from invading the inside of the motor through the vent hole.

It is preferable that the in-wheel motor further includes a driver connected to the lead wire for applying a current to the coil body; and a power supply connected to the driver, in which the in-wheel motor works as a generator such that, in a driving mode, the driver supplies electricity from the power supply to the coil body and, in a braking mode, the driver supplies electricity from the coil body to the power supply.

When braking is applied to the wheel, the in-wheel motor works as a generator to convert the rotational energy into electricity, and as a result, the in-wheel motor can function as a regenerative brake.

A second aspect of the present invention is to provide an electrically driven vehicle that is equipped with the in-wheel motor according to the first aspect of the present invention. The electrically driven vehicle refers to an electric car, a hybrid car, a motorcycle, a power-assisted bicycle, a wheelchair, etc.

According to the second aspect of the present invention, it is possible to provide the electrically driven vehicle that achieves effects similar to those of the first aspect of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional view showing an in-wheel motor according to a first embodiment of the present invention, which is cut into half along a shaft;

FIG. 2 is a front view of a wheel disk shown in FIG. 1, which is viewed from outside a vehicle; and

FIG. 3 is a vertical cross-sectional view showing an in-wheel motor according to a second embodiment of the present invention, which is cut into half along a shaft.

FIG. 4 is a vertical cross-sectional view showing an in-wheel motor according to a third embodiment of the present invention, which is cut into half along a shaft.

DETAILED DESCRIPTION OF THE INVENTION

A first embodiment of the present invention is hereinafter described in detail with reference to FIGS. 1 and 2. An in-wheel motor 1 according to the first embodiment is provided inside a wheel disk 5 of each of four wheels of an electric automobile, and a tire 7 is attached to an outer circumference of the wheel disk 5, thereby electromotively driving each wheel.

The in-wheel motor 1 includes: a stator disk 11 fixed to a shaft 9; a coil body 13 fixed to the stator disk 11; an outer yoke 15 disposed on an outer circumferential side of the coil body 13; a magnet 31 fixed on an inner circumferential face of the outer yoke; an inner yoke 17 disposed on an inner side to the coil body 13; and a brake mechanism 16 disposed on an inner circumferential side of the inner yoke 17.

In the present embodiment, a motor mechanism is configured with the coil body 13, the outer yoke 15, the inner yoke 17, and the magnet 31.

A hollow 19 for wiring is formed inside the shaft 9, and a lead wire 21 for applying an electric current to the coil body 13 passes through the hollow 19 of the shaft 9 and an inner circumferential side space of the outer yoke 15, and is connected to the coil body 13.

The stator disk 11 as coil body support member is discal, in which the shaft 9 is inserted through an aperture formed in the center of the disk to be fixed to the shaft 9 with a key 12.

The coil body 13 has a cylindrical shape, in which, for example, a copper plate is etched to be formed into a linear shape that is then insulated and superimposed as multiple layers. A car body side edge 13 a of the coil body 13 is fixed to the outer circumferential portion of the stator disk 11.

The outer yoke 15 has a cylindrical shape, in which a car body side edge 15 a of the cylinder is fixed to a cover disk 29, and a car body outer side edge 15 b is bent toward the inner circumferential side. The car body side edge 15 a of the outer yoke 15 is fixed to an outer circumferential portion 29 a of the cover disk 29 with a screw 27, and the cover disk 29 is discal, in which an insertion hole for the shaft 9 is formed in the central portion of the disk, and the shaft 9 is inserted through the insertion hole to be fixed to a bearing 25 with a screw 30.

The car body outer side edge 15 b of the outer yoke 15 is fixed on an inner surface of the wheel disk 5 via a spacer 26. Moreover, in the car body outer side edge 15 b of the outer yoke 15, a bent inner circumferential side edge thereof is fixed to a wheel-disk side edge 17 a of the inner yoke 17.

The magnet 31 is provided to the inner circumferential face of the outer yoke 15, and the magnet 31 is disposed to face the coil body 13. It should be noted that the magnet 31 is polarized to have a plurality of magnetic poles such that the magnetic poles vary in a circumferential direction.

The inner yoke 17 has a cylindrical shape, and is disposed to face the magnet 31 via the coil body 13. An inner circumferential face of the inner yoke 17 is fixed to a support disk 33, and the support disk 33 is fixed to a bearing 35 of the shaft 9. It should be noted that an oil seal 34 is provided to the bearing 35.

The outer yoke 15 and the inner yoke 17 are made of a magnetic material, and form a passage for magnetic flux.

In addition, in the present embodiment, the outer yoke 15, the inner yoke 17 and the stator disk 11 surround the outer circumferential side, the inner circumference and both ends of the coil body 13, and thus cover substantially the entirety of the coil body 13.

Furthermore, the outer yoke 15, the inner yoke 17, the support disk 33 and the cover disk 29 maintain the coil body 13 in a hermetically-sealed state.

The brake mechanism 16 is configured with a doughnut-shaped brake disk 37 and a caliper 39, the brake disk 37 being fixed on the inner circumferential face of the inner yoke 17. The caliper 39 is fixed to a discal caliper support disk 41 with a screw 43, and the caliper support disk 41 is fixed to the shaft 9 with a spline 45.

Moreover, a vent hole 47 is formed in the wheel disk 5 in a position facing a car body outer side edge 9 a of the shaft 9, and the outer diameter of the caliper support disk 41 is larger than that of the vent hole 47 of the wheel disk 5.

Next, driving, operation and effect of the in-wheel motor 1 according to the embodiment of the present invention are described.

The in-wheel motor 1 is driven in such a way that an electric current is applied through the lead wire 21 to the coil body 13, and as a result of an electromagnetic force arising against a magnetic field between the magnet 31 and the inner yoke 17, the magnet 31, the outer yoke 15 and the inner yoke 17 rotate as rotors with the coil body 13 serving as a stator, and the wheel disk 5 fixed to the outer yoke 15 rotates around the shaft 9.

When braking is applied to the rotation of the wheel disk 5, the brake disk 37 brakes through friction by operation of the caliper 39.

Since the in-wheel motor 1 according to the first embodiment is a motor of a so-called coreless type without an iron core, it is possible to provide an in-wheel motor that is more lightweight than a motor of a core type having an iron core such as those in the conventional art.

The inner yoke 17 and the outer yoke 15 are integrated, and the coil body 13 is disposed between the outer yoke 15, to which the magnet 31 is fixed, and the inner yoke 17; therefore, the outer yoke 15 and the inner yoke 17 can enhance the flux density of the magnet 31 acting on the coil body 13, and the driving torque can be enhanced.

The brake disk 37 is fixed to the inner yoke 17 that configures the motor mechanism of the in-wheel motor 1, and the brake disk 37 is disposed on the inner circumferential side of the inner yoke; therefore, the brake disk 37 can be disposed inside the inner yoke with a simple structure.

Since the brake disk 37 and the caliper 39 are disposed on the inner circumferential side of the coil body 13, the brake mechanism 16 can be installed inside the motor mechanism, and it is not required to provide space for installing the brake mechanism 16 in addition to the space for installing the motor mechanism, and thus the space for the motor mechanism is not restricted by the brake mechanism 16.

Since the outer yoke 15 and the inner yoke 17 cover the coil body 13, it is possible to achieve waterproofing of the coil body 13, and to prevent foreign matter from adhering thereto.

Furthermore, in the first embodiment, since the outer yoke 15, the inner yoke 17, the support disk 33 and the cover disk 29 maintain the coil body 13 in a hermetically-sealed state, it is possible to enhance the effect of preventing water and foreign matter from adhering to the coil body 13.

By taking in air through the vent hole 47 of the wheel disk 5, it is possible to cool the inside of the in-wheel motor 1. Since the caliper support disk 41 faces the vent hole 47, and the outer diameter thereof is larger than that of the vent hole 47, it is possible to prevent water and foreign matter from invading the inside of the in-wheel motor 1 through the vent hole 47.

Another embodiment of the present invention is hereinafter described, and in the embodiment to be described below, by assigning the same reference numerals to portions that achieve the same operation and effect as the first embodiment, descriptions of such portions are omitted, and points different from the first embodiment are mainly described in the following description.

A second embodiment of the present invention is described with reference to FIG. 3. In the second embodiment, the lead wire 21 described in the first embodiment is connected to a driver 51, and the driver 51 is connected to a power supply 53. The driver 51 is switched in conjunction with brake operation units 57 such as a brake pedal, and when a brake operation is performed, the driver 51 supplies electricity from the coil body 13 to the power supply 53 to cause the in-wheel motor 1 to work as a generator.

According to the second embodiment, when braking is applied to the wheel, the in-wheel motor 1 works as a generator to convert the rotational energy into electricity, and as a result, the in-wheel motor 1 can function as a regenerative brake.

The present invention is not limited to the aforementioned embodiments, and can be modified in various ways without departing from the scope of the present invention. For example, in the first and second embodiments, the vent hole 47 of the wheel disk 5 may not be provided. Moreover, in a case in which the vent hole 47 is provided, the position thereof is not limited to the position facing the car body outer side edge 9 a of the shaft 9, and the vent hole 47 may be provided in another position of the wheel disk 5, for example, a position spaced apart from the car body outer side edge 9 a of the shaft 9.

Moreover, in the second embodiment, resistance may be connected to the driver 51 to convert the rotational energy into heat for generating heat.

A third embodiment of the present invention is described with reference to FIG. 4. In the third embodiment, the magnet 31 fixed on the outer circumferential face of the inner yoke 17.

In the third embodiment an outer circumferential face of the magnet 31 may be wound with carbon fiber (not shown to prevent getting out by centrifugal force.

In the third embodiment, an inertial force of rotation is smaller than the first embodiment, therefore response of moving and stopping is better than the first embodiment. Also, in the third embodiment consumed energy is smaller than the first embodiment because of the inertial force of rotation is smaller than the first embodiment. 

1. An in-wheel motor installed inside a wheel disk of a wheel to rotationally drive the wheel around a shaft of the wheel by way of applying a current thereto, the in-wheel motor comprising: a coreless cylindrical coil body to which a lead wire for applying a current is connected, the shaft being inserted in an inner circumferential side of the coil body, the coil body supported at an inner car body end by a disk-shaped coil body support member that is fixed to the shaft; a cylindrical outer yoke that is disposed on an outer circumferential side of the coil body, and an outer wheel-disk end thereof is fixed to the wheel disk, an inner car body end of the outer yoke further being fixed to a cover disk that covers an inner car body side of the in-wheel motor and is journalled for rotation about the shaft; a cylindrical inner yoke that is disposed on an inner circumferential side of the coil body and has an outer wheel-disk end thereof attached to the outer wheel-disk end of the outer yoke, an inner car body end of the inner yoke further being fixed to a support disk rotatable around the shaft, wherein the outer yoke, the inner yoke, the support disk and the cover disk together rotate as a rotor around the coil body and provide a hermetic seal around the coil body so as to prevent water and foreign matter from reaching the coil body; and a magnet that is fixed to rotate with the rotor immediately adjacent a circumferential face of the coil body.
 2. The in-wheel motor according to claim 1, wherein a vent hole is formed in the wheel disk, and communicates with a space surrounded by the inner yoke, the support disk and the wheel disk.
 3. A motor comprising: a coreless cylindrical coil body including two ring-shaped ends, a hollow cylindrical wall defining the two ring-shaped ends and configured to encircle an external wheel shaft externally extending into the coreless cylindrical coil body, and a lead wire for supplying current to the coreless cylindrical coil body; a coil body support member located at one of the two ring-shaped ends of the coreless cylindrical coil body, configured to be fixed to the external wheel shaft, and fixedly supporting the coreless cylindrical coil body; a cylindrical outer yoke including a cylindrical wall having an inner and an outer cylindrical surface, loosely fit over the coreless cylindrical coil body, and configured to be fixed to an external wheel disk and to rotate together with the external wheel disk relatively to the external wheel shaft; a cylindrical inner yoke including a cylindrical wall having an inner and an outer cylindrical surface, loosely fit in the coreless cylindrical coil body, and configured to rotate around the external wheel shaft wherein the outer yoke, the inner yoke, the support disk and the cover disk together rotate as a rotor around the coil body and provide a hermetic seal around the coil body so as to prevent water and foreign matter from reaching the coil body; and a magnet fixed to rotate around the external wheel shaft and immediately adjacent to and directly facing the coreless cylindrical coil body.
 4. The in-wheel motor according to claim 1, wherein a vent hole is formed in the wheel disk, and communicates with a space surrounded by the inner yoke, the support disk and the wheel disk. 